Surgical snares are commonly utilized to remove polyps which grow on the colon. A surgical procedure called a polypectomy, is performed after the surgeon has inserted a fiberoptic colonoscope to observe the inside lining of the colon. A surgical snare which has a wire loop that is slidably housed in a sheath is inserted into the patient through the colonoscope. The surgeon may then observe through this colonoscope as the snare is extended from the sheath and maneuvered so as to encircle the polyp. The wire loop is then withdrawn into the sheath until it is closed somewhat tightly around the stem of the polyp, at which time an electric current is passed through the wire loop. Through the resulting heating of the wire loop, the polyp is then cut from the lining of the intestine and removed from the patient with a different instrument.
On occasion, complications occur during a polypectomy. One such complication is that the polyp may have a particularly thick stem, and the heated loop is unable to cut completely through it. The surgeon may attempt to loosen the wire loop and to reposition it. However, at times the wire loop itself is caught in the polyp stem tissue and cannot be released from it. When the surgeon is not able to cut through the polyp or release the wire loop from its entrapped position on the polyp stem, the patient must be taken to surgery for the removal of the polyp and the wire snare.
It is an object of the present invention to avoid the shortcomings of existing surgical snares. It is specifically contemplated that a surgical snare in accordance with the present invention be capable of being operated so that the wire scoop can be selectively opened to permit ready removal of the surgical snare in the event it becomes entrapped on a polyp.
It is also an object of the present invention to provide a surgical snare with a releasable loop which is relatively simple and inexpensive in construction, yet reliable and convenient in use.
In accordance with a preferred embodiment demonstrating objects and features of the present invention, a wire loop of a surgical snare is constructed so as to include a weakened or frangible region. When it is desired to open the loop so as to move it from its entrapped position on a polyp, an additional force is exerted on the loop to draw it further into the sheath. This causes the frangible region to break, thereby opening the loop and permitting the wire to slide free of the polyp.
In accordance with a second embodiment of the invention, a wire loop is constructed so as to fold back on itself, with the folded back end being captured inside the sheath. When the loop becomes entrapped on a polyp, it is extended out of the sheath somewhat further than during normal use, at which point the captured end of the loop is released, opening the loop and permitting its removal from within the patient.